Jerry Martin, Director of Bass Pro’s Professional Hunting Team, with a 140+ class Pope & Young trophy whitetail. Martin took the record book deer in south Missouri.
Earth’s four seasons occur, in part, because it wobbles slightly on its axis. That influence on seasonal weather affected human cultures ranging from Stonehenge, to the Olmec and Maya and to the present. The “wild kingdom” is strongly influenced as well.
Earth’s changing position as it wobbles on its axis causes shortening or lengthening of daylight depending on what solstice period seasonally applies. June 21st is the year’s longest 24‑hour daylight-period on our modern calendar. Losing three to five minutes of light a day after that date causes dramatic changes in a whitetail’s daily routine.
The process (governed by its pineal gland ‑ the so‑called “third eye” in vertebrates) is called photoperiodism. Photoperiodism influences the fall season’s leaf color, triggers the massive North American waterfowl migrations, tells the swallows when to return to San Juan Capistrano and , literally, gives impetus to every major migration on earth.
As days shorten, a substance secreted by the pineal gland (melatonin) releases sex hormones from the pituitary gland in whitetails. The male hormone, testosterone, then initiates a restriction of blood flow to summer’s velveted antlers. At this point, they begin to solidify.
The pineal gland serves as a transducer for photoperiod signals. It codifies light cues into chemical information throughout the whitetail’s body via its endocrine system.
When biologists removed the pineal gland during studies in certain deer, those deer then demonstrated a complete absence of reaction to the annual rut cycle.
Latitude influences photoperiodism. The closer to the equator, the less the Earth’s tilt, or wobble on its axis, influences the angle that the sun’s rays strike the planet’s surface. Therefore, this wobble causes the whitetail rut to progress mostly from northern Canadian latitudes in November south only to Texas in December.
Whitetails in the Florida Keys and the Tropics may never lose their antlers. Many biologists believe these southernmost whitetails breed year round. In other words, consistent periods of light in this zone do not generate photoperiodism activities generated in the earth’s northern latitudes.
From the last week of August through the first week of September, shedding bucks rub their antlers free from velvet. While the buck may breed now, the doe is not receptive to him yet.
While photoperiodism influences the doe’s estrous cycle, its timing for her to breed successfully occurs months later for her. While estrogen is the primary hormone responsible to initiate her mating urge, it is progesterone production that triggers her to accept the buck.
Her endocrine system does not produce progesterone till the egg is in position. Timing is critical because she is in estrus only 28 to 30‑hours.
Failing to successfully copulate now, causes her estrous cycle to recur every 25 to 30 days until successfully bred. Most studies show all North American breeding activity ceases by the following March regardless.
Approaching estrus stimulates a doe to urinate frequently. The urine and its endocrine products serve a pheromonal function. Pheromones are hormonal substances stimulating behavioral responses from an individual of the same species. In this case, the whitetail buck.
It is the scent of progesterone that triggers sexual aggression from the buck at the time of mating. That same production also increases the agitation of the doe. Until she produces this chemical, she cannot accept copulation.
While waiting for does to come into heat in November, bucks make rubs on saplings and larger trees. The process removes velvet from the now hardening antlers. It also exercises neck muscles preparing for future battles with peers for a lady’s favors.
Rubs serve another purpose. Buck’s deposit scent from forehead glands on the exposed wood of a rub leaving a personal message to other does and bucks alike. Combined with licking branches and scrape activity, deer leave “scent messages” throughout their territory.
Contrary to popular opinion, scrapes are not the “property” of one buck. Any buck passing by might use one. Occasionally, does do too. Rubs, scrapes and licking branches serve as scent communication centers for what is a loosely held herd animal.
In Missouri’s latitude, the peak of the rut normally occurs between November 10‑15. Decreasing daylight of that photoperiod triggers the endocrine system to release the hormones necessary for a doe to discharge an egg(s) into her uterus.
This is the most active part of the breeding season and the most productive time to hunt bucks. Female sexual pheromones discharged in the does’ urine informs both buck and doe when to breed. Both sexes actively pursue each other during this time to satisfy nature’s demands on them to multiply the species. Unfortunately, this is also the time of the year the most deer/auto collisions occur. The timing of the rut occurs so fawns will normally birth in spring when abundant food sources insure their survival. While egg fertilization occurs at copulation, implantation to the placenta in the uterus usually takes place about 30‑days later. This insures parturition (birthing) during spring’s surge of fresh tender young plant growth with which does will wean their new crop of fawns.
This is the normal procedure, as understood to this point, that nature uses to perpetuate the whitetail species. Bucks with the largest racks and body size are competitive enough that they do most of the breeding. While buck fawns can successfully copulate, most never get a chance to exercise the option because of the dominance-hierarchy that evolution programmed for this species.
Doe fawns (yearlings) might come into heat from December through February. Particularly if plentiful food supplies have them in good flesh. When this occurs, a second rut takes place until these female animals are bred.
All this activity can severely degrade a buck’s physical condition. With oak mast (acorns) usually significantly consumed by various wildlife by the end of February, the harsh winter weather after that time can be particularly hard on bucks. Their sexual activity often precludes healthier feeding priorities.
Knowing how and when the whitetail rut progresses from one stage to another helps buck hunters plan hunting strategy more successfully. For instance, using estrous deer lure too soon in the season may clue a savy heavy-racked buck about your devious intentions.